Electrical Machines Interview questions
A list of top frequently asked Electrical Machines interview questions and answers are given below.
1) What is a single phase Autotransformer?
A Single-phase autotransformer is a single winding transformer in which a part of the winding is common to both high-voltage and low-voltage sides.
2) What are the advantages of Autotransformer?
The advantages of autotransformer are as follows:
- Less winding material is required in case of the autotransformer.
- These transformers are not costly.
- These transformers are smaller in size.
- In Autotransformer ohmic losses and core losses are less.
- These transformers have high efficiency.
3) What are the disadvantages of Autotransformer?
The disadvantages of autotransformer are as follows:
- In case of Autotransformer effective impedance is smaller.
- In the case of open circuit winding, full voltage is transferred from the primary side to the secondary, and this can burn the equipment.
4) What are the applications of Autotransformers?
The applications of autotransformer are as follows:
- These are used for the interconnection of the power system at different voltage levels like 132KV and 230KV.
- In the distribution system, autotransformers are used to boost the supply voltage.
- Autotransformers can be used for starting induction motors and synchronous motors if it has many tappings.
- Autotransformers can be used as variac (variable a.c).
5) What is the general system requirement of Alternator?
There is a requirement of two types of system for the generation of e.m.f.
- The Magnetic system is required for the production of the magnetic field.
- Armature system is required for the houses of conductors on which the EMF is to be induced.
6) What are the advantages of Stationary Armature and Rotating Field System?
The advantages of the stationary armature and rotating field system are as follows:
- The coils of the stationary armature can be insulated easily.
- The cooling of the winding is more efficient.
- In the motor high peripheral speed can be achieved.
- In this Slip rings and brushes are not necessary, and we can easily supply the output current to the load circuit.
7) What is meant by Stator? What is meant by Rotor?
In AC/DC motor or Generator, the stationary part of the system is called the Stator, and the rotating components of the system, i.e., either in generator or motor is called the Rotor.
8) What are the Advantages of the three-phase motor over Single phase motor?
The advantages of three Phase motor over single phase motor are as follows:
- Starting Torques are higher.
- Improved speed regulation is there.
- Less vibration is there.
- The operation is quite.
9) What is the basic principle of operation of Alternators/DC generators?
Alternators/DC generators work on the fundamental principle of Faraday?s law of Electromagnetic Induction. This law states that when we move any current carrying conductor in a magnetic field, then an EMF is induced in it.
10) How to minimize the Eddy Current Losses?
Eddy current losses can be minimized by laminating the core and insulating the core from each other with paper or varnish.
11) What is meant by Turbo Alternators?
High-speed alternators are called Turbo Alternators. Because of the high speed of rotation, the diameter of the rotor is reduced, and the axial length is increased. In this two or four poles machine are used, and steam turbines are used as prime movers.
12) What are the various types of Rotor used in the Alternators?
The various types of a rotor are:
- Salient pole Rotor.
- Squirrel Cage Rotor.
- Wound Rotor.
- Cylindrical Rotor.
13) Define Pole Pitch?
Pole pitch is defined as the distance between the Centres of two adjacent poles. In which one pole pitch is equal to 180 electrical degrees. We can also describe it as the number of slots per pole.
14) Define Coil Span?
Coil Span is defined as the distance between the two coil sides of a coil. We can also express it in electrical degrees or many slots.
15) What is meant by full pitched winding?
Full pitched winding are those winding in which the coil span is equal to the pole pitch.
16) What is meant by short-pitched winding?
Short pitched winding are those in which the coil span is less than the pole pitch. These winding are also called as short-chorded winding.
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